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The Heathkit Build – Part 1 – Unboxing & Components

Ever wondered where some of the kit projects get their inspiration to strive for clear instructions, excellent documentation, and an overall fantastic DIY experience?

Heathkits were electronics kits popular in the late 1940s and 1950s. We have a mint AC Voltmeter kit that we will be building up over the next few days! We plan to document the experience and share it with all of you! Read on for more delightful photos and descriptions!

This Heathkit is for building an AC Voltmeter. Since the kit has been around for many years, some of the components may not work. Let’s get started and open up the box!

Here are all the contents of the box. Everything that we will need will hopefully be in here. It even comes with solder! Since solder does go bad over time, we’ll be using some more modern solder.

[Editor's note added: "More modern" in this case means recent-vintage solder of the same type and manufacture, which we happen to have in the lab.]

One of the neat things about a kit of this age are all the historic elements to it. This kit uses tubes, referred to as electron tubes on the boxes. The one on the left is a 6AW8A by Radio Corporation of America (RCA) made in Harrison, NJ. The one on the right is an EF184/6EJ7 by International Electronics Corporation (IEC) made in Melville, LI, NY (although on the tube it says made in Great Britain!)

The tubes inside are gorgeous. We don’t often have the opportunity to see these any more because they have been replaced by smaller solid-state devices. With that said, tubes were the key factor to bringing radar, television, broadcasting, sound recording, and much more to where it is today. Their exterior is made of glass with electrodes extending from the bottom.

This is a very old electrolytic capacitor! It is enclosed in a metal casing with its name and details embossed on it. Here’s what it says on it:

B-25-23

CODE MFD. W.V.

(semicircle) 80 150

(square) 40 150

(triangle) 20 150

FOR 85°C OPER.

GI 24066

I looked into this a bit more and found that the GI most likely stands for General Instrument. Wasn’t able to find any datasheet however.

More of the parts included with the kit. They are vintage and really colourful, check out the domino capacitors! Domino capacitors were used in the 40′s and 50′s, and you could determine their value by using the coloured circles. They are also known as Mica capacitors!

Here’s the pack of resistors with additional precision resistors. The precision resistors are the ones in the coloured shell. They are used for the turning knob, which will be discussed later!

Have you ever seen one of these? It’s a crystal diode! These crystal diodes are extra special because they are made of Germanium rather than Silicon. Germanium diodes are still used today because they have a different forward voltage. Cool eh!

Here is what Heathkit is known for- its instruction manual! It includes an envelope that you can send to request replacement parts, tips on how to solder, and fold-out pages of illustrations to follow. Here is a photo set of the instructions.

Since this kit is for an AC voltmeter, there is a very nice panel display that will be mounted on the front of the enclosure. Check out that vintage font! There is a clip on the back of the display between the two terminals. This has to be removed before use.

To wrap it all up, the Heathkit also comes with a sticker to identify your kit’s model and series number! This definitely adds an authentic touch.

After some assembly, the 4 lug terminal plug has all of its components added to it. It seemed throughout the instructions they kept changing their mind if they wanted to solder some of the leads to the lugs, so they are left unsoldered for now.

Getting the dial assembled was quite the challenge. The first part was to insert and tighten it all correctly so that the knob lines up with the lines. Afterwards several components have to be threaded through the lugs on the different decks.

One of the resistors, the precision 2.162K ohm, that had to be attached was actually missing. However thanks to the heaps of vintage components here, we found a similar one! The one we found was 2.15K ohm, making it within the tolerance of the original resistor.

Next up was starting to assemble the transformer box, with the capacitor. Except there’s kind of a big problem… the piece doesn’t fit the enclosure or the capacitor!

The instructions clearly do not show this predicament. Hmmm…

It’s definitely good to know that our Heathkit building experience is the real deal by having to find replacement parts, and in the case of the plate we will be making our own part! We can even complete the mail-in form for a replacement part and see what happens! Coming up in the next part will be more assembly, possibly testing the vacuum tubes, and more.

While looking around the internet for more information about Heathkits, there were a few really nice sites out there. Check them out:

36 thoughts on “The Heathkit Build – Part 1 – Unboxing & Components”

VERY cool project! Awhile back I worked on refurbishing a Heathkit IO-10 oscilloscope and later a Knight KG-250 integrated amplifier (both kits!).

I’ve been told by folks on the vintage audio forums that those old resistors may drift in value. Usually we replace capacitors for used equipment, particularly electrolytics.

I have no idea if old, unused resistors drift or if old electrolytics dry out, do you know? I have a pile of vintage components like those in the HK box… I wonder if should hang onto them. They’d be great on a beam robot. :D

You know – I wouldn’t use that capacitor anyway – The IM-21 was from around 1968 (best case) and that multi-stage capacitor has been ‘in the box’ a long, long time. You can replace it with normal, modern electrolytics, using ‘close’ values – like 22uf for 20uf.

The precision resistors should be in tolerance. Mica, ceramic, and film (if any) are usually long lasting. Electrolytics and paper capacitors (usually found in old radios) are almost always leaky or considerably out of tolerance.

I’m proud of you! These ‘unbuilt’ kits show up from time to time on eBay. Best thing for ‘em is to build it and have the fun.

I’ve rebuilt (and darn near re-kitted) a few of these from VTVMs on up to several of the Heathkit Amateur Radio products. They’re swell and lots of fun long AFTER the first build.

I built a few Heathkits up back in the day and they were all good test gear which went on to be used hard. What amazed me even back in the early 70s that the kits though dated technology (often late 1950s when i was born) was the amount of work that had gone into prepping all the instruction documents and the artwork (diagrams) was incredible. To me Heathkits were real kits and today we don’t see such presentation in a kit. I wish i still had those units i built up but like everything, they became considered old, superseded and so were chucked away. Pity.

I have to second his recommendation. The instructions for the Larson Scanner were clear enough that I handed the kit to a savvy 10 year old (he knew how to solder) who then was able to complete the kit easily. The pictoral nature of the instructions made the words hard to misinterpret. Now, on to Diavolino! (When time appears…)

In the early 1970s, DeVry Institute, in an effort to separate those of us who were Viet Nam era vets from our G. I. Bill money, offered a Home Entertainment Electronics Systems class that culminated with a free (paid for by the G. I. Bill) Heathkit 25 inch color television, arguably one of the most advanced televisions of the day.

I completed the course, which included building a rather basic O-scope, a VTVM (vacuum tube voltmeter), a lot of soldering training, and a rudimentary overview of all sorts of home entertainment electronics.

But I stuck it out, to get the television.

It was a hybrid set (both vacuum tubes and transistors) and built up on component PC boards – each of which would probably be replicated in a single IC today! Each completed board was used as part of the lessons, and various tests were performed on each board to both teach and ensure correct assembly. The set also included dot and crosshatch generators and degaussing coils

My wife was less than thrilled at my taking over the dining room table for the months this project took, and the UPS guy was not at all happy about delivering the 25 inch tube, or the huge flyback assembly, or the heavier transformers, but I finally completed the set.

I had a common wall between my family room and the laundry closet. I cut a hole in that wall, created a support for the weight of the set, and slid the whole thing into the wall, with only the bezel-equipped screen visible on the wall (all the electronics hung through the wall in the laundry area). I opted to buy the remote control kit from Heathkit, and would up with a 25 inch television mounted flat to the wall, operated by a remote control from my easy chair – amazingly similar to my current flat screen television set-up.

I’ve built many Heathkits myself. It seems strange that the capacitor mounting plate doesn’t match the capacitor. I would suspect that the former owner of that kit may have raided the box before you got to it. In any case I wouldn’t use ANY of the electrolytic caps in the kit. Install the large can for ‘looks’ but buy some radial or axil lead caps of modern vintage and use them instead of what came in the box. If you have a good capacitor tester / Rejuvenator you might want to test and restore the old ones, but they will only be trouble in a short while. I wouldn’t worry about the resistors, just test them with a good ohmmeter first.

It’s sad to hear about Heath’s demise. Their educational business was going strong for so long. I hope someone buys the name and continues the tradition.

Solder shelf life? Are you sure about that? Solder paste has a shelf life but I’ve never heard of a shelf life for a real coil of 60/40 rosin core solder. I’ve used some pretty old stuff myself, a quick Google search for solder shelf life found me a discussion where a guy is talking about using solder form the 60s with no problem on the first click!

About that cap… You haven’t applied power to it yet have you?!?! Electrolytics (new and old) rely on a coating of aluminum oxide to function correctly. When they sit unused for a long time the oxygen is released turning it back into aluminum. If you apply full power right away you can let the smoke out! What you want to do is slowly bring up the power and the electricity will cause the aluminum to oxidize again.

What a lot of people do that are in to restoring old equipment is use a variac. That is a sort of variable transformer (really more of an autoformer) that allows you to change the line voltage going into the device. Just start it low and turn it up slowly. I’m not too well versed on how slowly to turn it up, Google it. You are looking for "capacitor reformation".

Since yours isn’t assembled yet (or is it?) an easy way to accomplish the same thing is to just hook each capacitor to a variable DC power supply (remember, there is more than one in that big can). Again, start the voltage low and slowly turn it up to it’s rated voltage or at least to the voltage it will actually see in the circuit.

Easier yet… just skip all that and use a new part. With those big cans some people go out of their way to make it authentic. They cut the can open, pull the guts out and mount the new capacitors inside. Then you have to find a way to re-seal the can. Or.. you can just mount the can but not hook it up and solder the new capacitors in place under the chassis. That way everything looks authentic above the chassis, just don’t look below!

However you handle your old caps… good find on the unbuilt Heathkit! There are collectors falling all over themselves for these things!

If you ever look at a spool of solder– one made for use in industry –it will have an expiration date. And that date always seems surprisingly soon, to us.

Here in Silicon Valley, we regularly purchase solder (including flux-cored 60/40) that is discounted because it is sold after its stamped expiration date– sometimes as much as five years past. To us, this is just “a good deal.” We’ve had some spools work better than others, and it would be very hard for us to *prove* that one is “bad” because it’s old.

None the less, the solder manufacturers are explicitly clear on the subject.

Kester, one of the most important manufacturers, says “Flux cored solder wire has a limited shelf life determined by the alloy used in the wire. For alloys containing more than 70% lead, the shelf life is two years from date of manufacture. Other alloys have a shelf life of three years from date of manufacture.”

Alpha, the manufacturer of the solder included with this kit, says of (at least one of their) flux-cored solders, “If >36 months from manufacture, please submit sample to Cookson Electronics Assembly Materials for testing.”

Maybe that explains it. I can imagine that in a factory where millions of connections are being soldered per day even a slight decrease in solder quality could result in a lot of rework. If for example, in one connection of 1000 the solder doesn’t flow correctly the first time in a production environment for some board with say 500 connections then that could mean that half of the boards come out non-working. That would be a huge problem.

For a typical kit builder however a really busy day would be what, 150 solder joints? And each solder joint would be given personal attention, one at a time by the builder. If it doesn’t go right on the first try he/she would just reheat the joint or if that doesn’t work then maybe remove the solder with wick or a sucker and do it again. This will probably occur much more often due to other reasons, soldering tip needs cleaned, fingerprint on the copper, hand tremor, etc… anyway. Will the user of decades old solder even notice the difference? If so is it enough to really matter?

Rosin / liquid core solder probably does have a limited shelf life. It’s not clear just how stable that liquid in the middle is. It’s probably fine, but after a few decades it might dry out or crystalize or something.

P.S. This brings back my metal shop days of slopping on the flux with a brush, then using a hot iron, sort of like a branding iron, to lay down the bead of molten solder. The smell was delicious which means it has probably rotted my brain.

My brother was assembling a Heathkit oscilloscope, and he had me help. I was all of five or six years old, but could see colors. My brother was red-green colorblind, and couldn’t properly identify the resistors. He would tell me which colors he needed, and I would locate them for him.

He finished the ‘scope, and really didn’t use it at all. Years later, as a senior in high school (1975), I used it to measure the speed of light.

Thanks for the trip down memory lane. Built several of them in the 60′s and 70′s. Used to call them ‘griefkits’; They invariably didn’t work the first time you powered them up. No better way to develop one’s troubleshooting skills.

My Heathkit experience was building a VT52-compatible monitor with a friend, for his computer. It was a pretty nice monitor for that time (1979-1981, roughly) – it had real descenders on the characters, because it wasn’t using 5×7 dots. (I did the soldering, he did the tube installation and the heavy lifting.)

The expiration date on solder is news to me. I’ll have to pull out my ancient (1978) roll of Kester eutectic….

The reason that some of the component leads are soldered and others just twisted around the lug is that Heathkit would only tell you to solder after the last component was added to the lug. That way you wouldn’t be trying to put a lead through a hole that already had solder.

They will all be soldered by the time the kit is complete.

I second the comments that the electrolytic and paper capacitors are probably no good. If you use them, watch the temperature of the transformer for the B+ (high voltage supply to the tubes), as leaky capacitors may overload the supply and burn up the transformer. It’s a common problem with old radios.

My dorm had a Heathkit color TV in the lounge. We were a STEM school, so it made sense to have a committee build a TV rather than spending more to buy a pre-assembled one.

I never got to build anything by Heathkit. I got off brand transistor radio kits and the like that my dad picked up on Radio Row which was later replaced by the World Trade Center. The instructions were actually pretty good, though you didn’t learn any electronics, just the mechanics. The components usually worked, but not all that well. I had trouble with the two transistor radio kit and I remember my cousin, who had built his own TV from parts, not a kit, told me to bite down on the earphone cord. This actually worked, but who wanted a radio that you could only listen to with a wire in your mouth? Does anyone else remember this trick? Did it change the capacitance or resistance?

What a joy to see. My dad, an EE, built a Heathkit color television kit that had a motor drive for changing channels. It also had a cool tip-out panel with a pile of pots for adjusting picture quality, which me and my brothers messed with constantly. Every time it broke, he took out the manual and diagnosed and fixed it.

On his own, he also built a couple clocks, a calculator, and a countdown timer for darkroom processing.

Although I never got to build a heath kit, I remember salivating over the catalogues. The really cool kits that I wanted where always too expensive for my pocket money. It seemed Heathkit where selling kits of unbelievable scientific items. If they where about now I would expect them to be selling ‘Build your own particle accelerator’ kits. I would love to see them come back. Now, I think, would be the time. The maker movement is growing. I know there are a growing number of kit producers but it would be nice to see Heathkit among them. Well….. Go E.M.S labs and all the other kit producers out there. Make out kids the Engineers for the future.

Just picked up a Heathkit IO-4105 Oscilloscope (Unbuilt) off of Amazon and look forward to the build. Your advice on replacing the capacitors and testing the resistors was what I was planning. Can I assume and tubes will be ok?